Tensile engineering offers design flexibility in many ways that other building materials cannot. They are lightweight, strong and durable systems which offer benefits such as diffusion of light, acoustic dampening and the ability to span large areas uninterrupted. Their versatility from shade canopies to wall and ceiling panels gives these structures the ability to adapt across all industries.
Tensile Structures are formed by tensioning fabric across or around an aluminium or steel framework. True tensile fabric structures are those in which every part of the fabric is in tension. The fundamental rule for stability is that, a tensioned fabric structure must curve equally in opposite directions; giving the canopy its 3-dimensional stability. Fabric can achieve far greater spans than conventional building materials, with minimal supporting structure.
Greater translucency and dynamic, organic shapes bring the feeling of outside, inside, as well as providing shade and protection from the weather.
Tensile structures generate what are known as ‘live loads’ instead of the static ‘dead loads’ of traditional roofing materials. Modern architectural fabrics offer increased stability and longevity often 20+ years.
Our library houses a range of 3d .dwg files that you may download and use, for free.
All we ask is that you leave a few contact details with us, before we grant you access.
Once you have submitted the form, you will receive an email that contains a link to our online library, where you may download relevant files and use them to further your eduction on tensile structures or detail them in project proposals, etc.
We are currently reviewing and updating our CPD course.
Please sign up to our mailing list for more information on when it will be available again.
Forms of a Tensile Structure
To ensure that fabric is a stable building material we need to create a ‘double curvature’ into the form of the structure. This gives it rigidity, allowing it to deal with any wind and snow loads that will be applied to it. This curvature is achieved by patterning fabric panels, bonding them into a 3-dimensional shape and then placing them under tension.
What is tension?
Tension is the force used to pull the structure of a material apart. It is the most efficient way of using any material because it utilises the whole cross section at maximum efficiency. For example, a stick will break under compression or bending, long before it would be pulled apart by tension. Tension loads maximise the load capacity of materials and requires the least material.
What is a tensioned fabric structure?
Tensile fabric structures are those in which every part of the fabric is in tension. The fundamental rule for stability is that, a tensioned fabric structure must curve equally in opposite directions; this gives the canopy its 3-dimensional stability. This is often referred to as ‘double curvature’ or an ‘anticlastic form’ and mathematically it is known as a ‘hyperbolic paraboloid’. If we place flat panels under tension, they will stretch over time and then become unstable as the wind catches them – potentially coming away from their fixings in particularly strong winds. Flat structures can be made but they require much stronger steel structures.
Although tensile structures can often look beautifully simple, they are highly engineered designs that encounter lots of design considerations. With that in mind here is a list of things to consider when choosing your tensile structure or product.
What you intend to use you structure for will influence the shape of the structure you require. For the greatest structural stability, a canopy’s shape should have anticlastic curvature in it, usually expressed as a barrel vault, cone, or hyperbolic paraboloid. This give the structure its distinctive organic form, and more symmetrical shapes will result in lighter steelwork and smaller foundations.
Triangles do not work as tensile structures because, when tensioned, they will always be flat – this makes them very inefficient when dealing with wind and snow loads.
Depending on the use of the structure there may be pe engineered structures developed within our Signature Products range which can be customised and modified. This can help lower costs and speed up delivery and installation.
These are often larger than expected and provision should be made for large blocks of concrete to be used. Tensile structures are effectively large sails very capable of pulling a ship from one side of the Atlantic to the other, although in this application they need to stay very firmly tethered to dry land!
The same thing applies if the structure is to be fixed to an existing building: can connections be made at points where the imparted loads can be managed effectively? Tensile structures usually need to fix directly into a building’s frame, rather than simply into masonry.
What is the distance from the coast, the altitude above sea level, is it an urban or rural environment? These things affect the wind and snow loads that can be expected to act upon the structure.
There are many considerations here: fire rating, light transmission/reflectivity/absorption, life expectancy, colour, flexibility (for ease of installing larger canopies), cost etc. The number of tensile fabrics available on the market means that a material can always be found to meet your specification requirements. For more information on the fabrics available and their properties visit our materials page.
Tensile fabric structures are comparative with polycarbonate structures and prove more cost effective than glazed structures. With value added engineered incorporated into our deigns, particularly efficient structures often work out to be less than this, as do many pre-engineered designs.
Tensile fabric structures can be very environmentally friendly options for coverage. Most architectural grade fabrics can be recycled, and some are made from highly sustainable materials; silicone coated woven glass fabrics are produced wholly from silicon. Effective water management also means rainwater harvesting can often be incorporated in to designs.
The curving shapes of tensile canopies mean that rainwater can usually be made to run off at pre-determined points. From there, it can either free-drain or be collected and channelled through the structure’s framework for connection to site drainage.
It is often a requirement, during the installation of tensile structures, to lift single pieces of fabric that are many thousands of square feet, or pieces of steel that weigh hundreds of pounds. The access equipment needed for this can be large and heavy and the installation of a tensile structure should be scheduled accordingly.
To maintain their best appearance, tensile fabrics should be cleaned every 12 months with warm soapy water. Provision for access to carry this out should therefore be designed into the structure, often by inclusion of lugs for harness connections. This enables appropriately qualified riggers to walk safely on the canopies, which can easily support the weight of several people.
If you have an existing fabric architecture structure that requires an inspection, report or maintenance work, please get in touch with us and we can provide you with a maintenance quote.
